Semiconductor chips are more and more reduced in size and thickness and are more and more three-dimensionally integrated so as to achieve reduced size and weight, higher functions, minimized power consumption, and any other advantages. The semiconductor chips as above are produced by patterning circuits on a wafer, backgrinding the patterned wafer to thin the wafer, and dicing the thinned wafer. The wafer after thinning is very fragile and is susceptible to failure (breakage) upon processing such as grinding and dicing and upon transportation. To eliminate or minimize this, the wafer is processed and transported while being temporarily secured typically to a supporting substrate and being protected.
A waxy adhesive has been used for the wafer temporary securing (Patent Literature (PTL) 1). The waxy adhesive, however, has a low softening point or melting point and flows to fail to secure the wafer upon a high-temperature process performed typically when film deposition in patterning is performed via vapor deposition and when the wafer is transferred from the temporary-securing substrate to a wafer for integration. Another known adhesive is a heat-sensitive adhesive including a pressure-sensitive adhesive and a side-chain crystalline polymer (PTL 2 and PTL 3). Disadvantageously, however, this adhesive also flows and fails to secure the wafer in a high-temperature process. Yet another known adhesive is an adhesive that is cured, shrunk, and deformed by the irradiation typically with an ultraviolet ray, and the adherend is thereby removed. Unfortunately, however, this adhesive applies stress to the wafer upon removal and causes warping and/or fracture of the wafer.